This research involved a new process developed to support the rapid development of computer-aided design (CAD) geometry to model personal protective equipment (PPE). The armor was developed and used in modeling and simulation for analysis of the Tier 4 Soldier Protection System (SPS) compared to the Improved Outer Tactical Vest (IOTV). The goal of modeling the PPE CAD geometry was to create a representation of the armor system to scale relative to the Operational Requirement-based Casualty Assessment (ORCA) man model and place the armor system in the correct location relative to anatomical landmarks.

To reduce production time and increase accuracy of armor placement for vulnerability/lethality modeling, the US Army Research Laboratory’s Survivability/Lethality Analysis Directorate explored a new process for CAD model creation. This methodology included CT scanning using the General Electric BrightSpeed model and placing the physical armor system on a foam manikin representative of ORCA man. This foam ORCA-man surrogate (referred to as foam manikin) is optimal for scanning given it is lightweight and has low density. It also provides real-life dimensions and fit of the armor system to the ORCA-man geometry, which is used for vulnerability/lethality modeling.

Four systems were CT-scanned on the foam manikin: a medium IOTV, the large IOTV pelvic under garment/pelvic outer garment (PUG/POG) system, a medium SPS, and a large SPS. Two scans for each system were conducted. The first included all pieces of the system: the cloth vest holding the hard plates and ballistic soft armor, the PUG/POG; the second included only the ballistic soft armor (outside of its cloth lining) placed on the foam manikin. This latter scan was to prevent scan artifact and material bunching or separation of soft armor layers. Only the large PPE systems were segmented, as those were being created to support SPS live-fire evaluations. Figure 1 displays the full IOTV and SPS systems on the ORCA foam model.

Figure 2 - IOTV soft armor in Mimics software showing soft armor (red mask) placed on ORCA foam model in coronal slice (left) and rough soft armor geometry created from segmentation (right).

The CT scans resulted in Digital Imaging and Communications in Medicine (DICOM) formatted data. DICOM format is the international standard for medical imaging. The DICOM data and header files provide a series of stacked images along with metadata and measurements. For this process, the DICOM files were used to understand and create a 3-D model of each armor system by examining and defining layers of materials. After the scans were collected, they were analyzed, segmented, re-topologized, and finalized as CAD geometry.

To segment the CT scans, each respective set of the DICOM images was loaded into Materialise’s Mimics analysis software. Each PPE component was segmented into individual pieces, which together define the entire armor system. Segmentation is the process of applying a 2-D mask to each image in the DICOM image series to define the armor system object of interest. The defined 2-D mask was then used to generate 3-D geometry, as shown in Figure 2. The 2-D masks were created using a series of density selection tools as well as manual selection tools. The masks often have high resolution and artifact interference that result in initial geometry that requires further refinement to ensure the model is smooth and watertight.

This work was done by Autumn R. Kulaga, Kathryn L. Loftis and Eric Murray for the Army Research Laboratory. For more information, download the Technical Support Package (free white paper) below. ARL-0227

This Brief includes a Technical Support Package (TSP).
Development and Verification of Body Armor Target Geography Created Using Computed Tomography Scans

(reference ARL-0227) is currently available for download from the TSP library.

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This article first appeared in the August, 2020 issue of Aerospace & Defense Technology Magazine.

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